CAREL's Enrico Boscaro illustrates at ASHRAE Malaysia seminar the potentials of Indirect Evaporative Cooling technology as an energy savings instrument in cooling applications, in particular for the Make up Air handlers sector.

1. ENERGY SAVING BY EVAPORATIVE
COOLING IN AHUs
This document and all its contents are for Carel internal use only and strictly CONFIDENTIAL
All unauthorized use, reproduction or distribution of this document or the information contained in it,
by anyone other than Carel employees is severely forbidden
Enrico Boscaro
CAREL Industries SpA (Italy)

2. We are specialists in control technologies
for air-conditioning & refrigeration.
Our products are designed to bring value to the customer
offering energy savings solutions.
This document and all its contents are for Carel internal use only and strictly CONFIDENTIAL
All unauthorized use, reproduction or distribution of this document or the information contained in it,
by anyone other than Carel employees is severely forbidden

3. 1100+
Employees
19
Subsidiaries
3,700+
Customers
6,200
Part numbers
7 Mln
Pcs per year
203 Mln€
Turnover
7
Production facilities
CAREL in snapshot

4. Our key strategies
We offer
integrated
solutions for
vertical
applications
We innovate to
achieve higher
energy saving
We continuously
improve our
operating
performances
and ensure
financial solidity
We want to be
close to the
customers for a
better
understanding of
their needs
We operate
globally with the
same world-class
manufacturing
standards
We are
specialists in
HVAC and
Refrigeration
This document and all its contents are for Carel internal use only and strictly CONFIDENTIAL
All unauthorized use, reproduction or distribution of this document or the information contained in it,
by anyone other than Carel employees is severely forbidden

5. Index
1. Basics of Evaporative Cooling DEC and IEC
2. Use of IEC for Make up Air Handling Units
3. Different systems for humidification

6. Index
1. Basics of Evaporative Cooling DEC and IEC
2. Use of IEC for Make up Air Handling Units
3. Different systems for humidification

7. Natural water evaporation & cooling
• Water naturally evaporates when in contact with air
• It requires energy: the latent heat of vaporization
• Latent heat of vaporization  690 W/(L/h)
• This heat is drawn also from the air, which is
humidified and cooled (evaporative cooling)

8. Evaporative Cooling
100 kg/h
The principle: a potential for Energy Saving

9. Make up Air handling Units
Exhaust air
Return
air
Supply
air
Fresh air
Mechanical Ventilation for buildings

10. Cross Flow Run around coil Thermal Wheel
Heat recovery
Exhaust
air
Fresh air
Air after
recovery
Bypass damper
Fresh air
Exhaust
air
Water coils
pipes Pump
Exhaust
air
Fresh air

11. Direct Evaporative Cooling
25°C
50%rH
30°C
30%rH
» Direct effect on the main airflow
» Whenever it is possible to raise the humidity of supply air

12. Indirect Evaporative Cooling
» Use of a air to air heat exchanger
» Exhaust air saturation
30’000 m3/h
25°C
70%rH
25°C
50%rH
28°C
55%rH
18°C
100%rH
100 kg/h
η
35°C
40%rH
100kg/h of water
1kW electric power
heat recovery ε 58%,
Rec= 42kW cooling (12 tons)
≈15kW electric saving (EER 3)

13. Index
1. Basics of Evaporative Cooling DEC and IEC
2. Use of IEC for Make up Air Handling Units
3. Different systems for humidification

14. N°6 AHU
W= 2400 mm
H= 2010 mm
Air flow= 35.000 m3/h
Hum= 250 kg/h
Evap. Cool. = 100 kg/h (68 kW)
Evaporative cooling at
Hotel Parchi del Garda - Verona - Italy

15. 10.000 €
of
SAVING
per year!
Evaporative cooling at
Hotel Parchi del Garda - Verona - Italy

16. What about regions with high humidity?
KUALA LUMPUR
Room @ 24°C 55%
Cooling all year long for
humidity control
7960 h of potential recovery

17. AHU application: heat recovery actual convenience

18. Heat exchanger “wet and “dry” efficiency
o It depends on materials and geometry
o Trenewal OUT at a given efficiency decreases with
lower Treturn IN
o Reduce Treturn IN temp with Evaporative Cooling up
to the wet bulb temperature
o Contact evaporation is an additional phenomenon that
is relevant but it has to be possible wetting the surface
o Fin pitch VS water drop dimensions ( air pressure
drops)
o Special coatings can grant an excellent distribution of
water film while giving resistance to softened water
𝜀 =
𝑇𝑟𝑒𝑛𝑒𝑤𝐼𝑁 − 𝑇𝑟𝑒𝑛𝑒𝑤𝑎𝑙 𝑂𝑈𝑇
𝑇𝑟𝑒𝑛𝑒𝑤𝑎𝑙 𝐼𝑁 − 𝑇𝑟𝑒𝑡𝑢𝑟𝑛 𝐼𝑁

19. • The HE cannot be wet
• Non-evaporated drops must be collected and drained
• Drop separator (30 Pa) and drained drop pan are
required before the heat exchanger
• Space is necessary for absorption
IEC with “dry approach”

20. Simulation for KL
KUALA LUMPUR
Number of hours for convenient recovery
- standard: 5305 h
- With IEC: 8760 h
24/7 operation at maximum air flow
Potential saving

21. SAVING ENERGY IS SAVING WATER
To yield 1 kWhcooling, a chiller–based system uses:
EERSI = 3 kWcooling/kWelectric
[e] = 0.3 kWhelectric
(= 1 / 3)
Combined value for the water withdrawal of power plants : 40.2 L/kWhelectric
1 kWhcooling generated by a chiller system requires: [a] = 13.4 L of mains w.
(= 1/3 x 40.2)
Heat exchanger’s efficiency: 75% 75%
If IEC does 1 kWhcooling to the outdoor air, the cooling of the
exhaust air is:
and the evaporated water in the exhaust air is:
1 L of evaporated water  0.69 kWhcooling
1.3 kWhcooling
(= 1 / 0.75)
1.9 L
(= 1.3 / 0.69)
The amount of mains water supplied to the water-spraying
system is:
WUE of the water atomizer is equal to 80%
[c] = 2.4 L
(= 1.9 / 0.80)
Input energy to IEC @ 10 W/(L/h) [d] = 24 Wh (= 2.4 x 10)
Input energy saved [e-d] 0.309 kWhelectric/kWhcooling
Mains water SAVED with IEC [a-c] 11.0 L/kWhcooling

22. Index
1. Basics of Evaporative Cooling DEC and IEC
2. Use of IEC for Make up Air Handling Units
3. Different systems for humidification

23. Evaporative Cooling
Wet media Atomization with
compressed air
Different techniques
Air washer
Atomization with pressurized water

24. Water atomizers: description
• They spray water in very tiny drops (5-50 µm)
• The smaller the drops, the wider their total
surface, the stronger the evaporation and the
evaporative cooling
• Small drops is better!
• Input power 0.5-10 W/(L/h) to yield 700
W/(L/h) of cooling

25. Evaporation in AHUs/ducts
• Tiny drops fly with the air, do not fall
• Evaporation takes time, thus some drops may not fully
evaporate before the first device downstream (coil,
blower, etc.)
• Evaporation efficiency η = evaporated/sprayed water =
50%-95% depending on models and conditions
°C before g/kg before m³/h m/s µm
         
η          
Key:
 = the characteristic increases
 = the characteristic decreases

26. WUE: Water-Usage Effectiveness
• WUE = evaporated water / input mains water
• WUE = (evap.’d w. / sprayed w.) x (sprayed w. / input mains w.)
• Typ. WUE with RO system: 10% to 48%
• Typ. WUE with softener: 48% to 95%
Water
treatment
Supply waterMains water Drain

27. OptiMist: atomizing evaporative cooler

28.  Integrated controller with display
 Continuous modulation with VFD
 Stainless steel vane pump for long lifespan
 Optimal atomization @ 15bar
 Optimal absorption efficiency
 Wide modulation range with two steps
 Wide capacity range (20…1000kg/h)
 Pressure and temperature controls (and safety)
 Integrated T, TH, TF, etc regulations
 Anti freezing
 CE and UL certification
optiMist: atomizer for evaporative cooling

29.  Stainless steel manifolds, pipes and nozzle’s heads
 Very easy to assemble thanks to compression fittings
 Wide rangeability with 1 or 2 uniform steps
 Mechanical or electric drain valves
 Negligeble pressure drop
 Up to 1000kg/h capacity
 Demineralized, softened or tap water
 High hygiene (automatic drainage, washing, UV)
optiMist: atomizer for evaporative cooling

30. Advantages of atomizers compared to wet
media for IEC
• Lower pressure drops
• Hygene
• Possibility to exploit «wet efficiency»
• Control

31. Wet media on return air
Return air
Flow 30000 m3/h
Speed 3,1 m/s
Dp tot 941 Pa
Dp with wet media 1021 pa
Absorbed power(plug fan) 13,11 kW

32. Atomizer on return air
Return air
Flow 30000 m3/h
Speed 3,1 m/s
Dp tot 941 Pa
Dp with wet atomizer 971 pa
Absorbed power(plug fan) 12,46 kW
In one year (8000 h) : 8000x 0,65 kw (difference) x 40 sen/kWh = 2000 MYR per year

33. Hygiene: the HE is not sealed (or special version is required)

34. Possibility to use «wet efficiency»
• + 15-20% cooling effect achievable

35. Modulation for control purposes
• Demand control ventilation can make the air
flow vary consistently (50-100%)
• The capability to modulate of atomizers helps
to control supply temperature (inertia of wet
media and impossibility to modulate)
CO2
100%
0 %
FANS
FAN MIN
SPEED
Variable air
flow depending
on air quality

36. Conclusions
• Evaporative cooling is a technology that can lead
to remarkable Energy Savings
• Humidity increas has to be possible so this
technology doesn’t work in high humidity
regions
• The IEC has a real potential for the area for
Make up Air handlers
• There are different adiabatic technologies that
should be evaluate in the TCO perspective